MI5 has issued a warning to UK businesses that spies in China are conducting a campaign of cyber-espionage against them.

Martin Jordan, principal advisor of IT advisory services at KPMG, said that MI5 — through its branch the Centre for the Protection of National Infrastructure — has been monitoring activity emanating from China and it has noticed an upsurge in electronic espionage attempts made or launched against a lot of UK companies.

More than 1,000 letters were subsequently sent by the director general of MI5 to the heads of UK business yesterday, according to Jordan, warning them spies are targeting financial information relating to deals that may occur and involve Chinese companies.

Jordan said the Chinese cyber spies are trying to find out the financial limits of such deals to subsequently push UK companies to pay out the maximum or receive the minimum amount of money within such deals.

A Home Office spokeswoman said that the Home Office and MI5 will not comment on any "leaked private correspondence".